Molecule

Drug Groups

approved; investigational

Description

An opioid analgesic with actions and uses similar to those of morphine, apart from an absence of cough suppressant activity. It is used in the treatment of moderate to severe pain, including pain in obstetrics. It may also be used as an adjunct to anesthesia. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1092)

Indication

For the treatment of moderate-to-severe pain.

Pharmacology

Oxymorphone is a semi-synthetic opioid substitute for morphine. It is a potent analgesic. Opioid analgesics exert their principal pharmacologic effects on the CNS and the gastrointestinal tract. The principal actions of therapeutic value are analgesia and sedation. Opioids produce respiratory depression by direct action on brain stem respiratory centers. The mechanism of respiratory depression involves a reduction in the responsiveness of the brain stem respiratory centers to increases in carbon dioxide tension and to electrical stimulation.

Toxicity

Oxymorphone overdosage is characterized by respiratory depression, extreme somnolence progressing to stupor or coma, skeletal muscle flaccidity, cold and clammy skin, and sometimes bradycardia and hypotension. In a severe case of overdose, apnea, circulatory collapse, cardiac arrest, and death may occur. Intravenous mouse LD₅₀ is 172 mg/kg.

Affected Organisms

Biotransformation

Oxymorphone undergoes extensive hepatic metabolism in humans. After a 10 mg oral dose, 49% was excreted over a five-day period in the urine. Of this, 82% was excreted in the first 24 hours after administration. The recovered drug-related products contained the oxymorphone (1.9%), the conjugate of oxymorphone (44.1%), the 6(beta)-carbinol produced by 6-keto reduction of oxymorphone (0.3%), and the conjugates of 6(beta)-carbinol (2.6%) and 6(alpha)-carbinol (0.1%).

Half Life

1.3 (+/-0.7) hours

Elimination

Oxymorphone is highly metabolized, principally in the liver, and undergoes reduction or conjugation with glucuronic acid to form both active and inactive products. Because oxymorphone is extensively metabolized, <1% of the administered dose is excreted unchanged in the urine.

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